|Submission Date||Nov. 27, 2019|
University of Wisconsin-Milwaukee
IN-16: Campus Water Balance
|0.50 / 0.50||
Sustainability Planning & Policy Analyst
Office of Sustainability
A brief description of the methodology used to calculate the campus water balance:
UWM used the guidance as set forth in the Alliance for Water Stewardship's International Water Stewardship Standard Version 2.0. Water balance was calculated for both the Main Kenwood campus site, the School of Freshwater Sciences site, as well as the catchment.
The following equation can be used to describe each site's water balance:
P + Wi + Hi = R + E + Web + Wes + He + ΔSg + ΔSc
P is precipitation
Wi is potable water supplied by Milwaukee Water Works
Hi is heat plant intake water
R is streamflow
E is evapotranspiration
Web is sewage discharged from buildings into municipal combined sewers
Wes is stormwater runoff discharged from impervious surfaces like rooftops, parking lots, and sidewalks into municipal combined sewers
He is heat plant effluent discharged to Lake Michigan
ΔSg is the change in storage in groundwater
ΔSc is the change in storage in cisterns
A brief description of how the institution’s water use compares to the natural water balance of the campus:
Potable Water supplied by Milwaukee Water Works: Treated potable water is supplied to the University through MWW's distribution system. This system is highly reliable. Despite occasional water main brakes, which are generally repaired by municipal and/or university staff within a matter of hours, service disruptions do not present a threat to water balance at UWM.
The volume of water used is driven by multiple factors, including the activities of students, staff, and faculty, the efficiency and usage levels of HVAC equipment, and, particularly at SFS, water-intensive research activities. Each of these factors are complex but are ultimately within the control of the University. Since 2005, SFS has used an average of 265,175 CCF per year, and main campus has used an average of 113,554 CCF per year. Annual variations in water usage rates are discussed further in the next section.
Because UWM uses a large volume of water, it is possible that Milwaukee Water Works could impose a maximum usage cap during times of peak demand. There are no such rules in place now, though we note it here because it could become a consideration in the future.
Heat plant intake and effluent: UWM uses a pumping station to withdraw water from Lake Michigan which is used for heating and cooling at the heat plant on Main Campus. It is a non-contact closed system, so effluent should theoretically match plant intake, as expressed by the following equation:
Hi = He
Streamflow: No streams flow through either site, despite the proximity to the Inner Harbor and Milwaukee River. Any precipitation that falls on the sites flows into storm sewers, infiltrates to groundwater, or is returned to the atmosphere through evapotranspiration.
Evapotranspiration: This factor is difficult to measure and is not considered an important factor in this report. Despite large volumes of water evapotranspiring from the campus, particularly from natural areas like Downer Woods, it does not contribute directly to the water-related challenges identified here and is therefore omitted from our consideration.
Sewage discharge: Virtually all the water that is discharged into municipal sewers originates from the municipal supply. At the time of this writing, no rainwater recycling for indoor use is practiced on a significant scale at either site. Therefore, the municipal water balance can be expressed by the following equation:
Wi = Web + C + D
C is consumptive use, or water that is supplied to buildings but is not returned to the sewer system.
D is water directly discharged into waterways.
Main campus has no direct discharges, so any difference between water supplied and water discharges is assumed to be consumptive use. Since 2011, when tracking of these data began, the main campus has averaged 3.4% consumptive use.
SFS directly discharges a large portion of its water to the Milwaukee Harbor. While it is assumed that some small percentage of water is lost to consumptive use, this cannot be differentiated from discharges to the harbor, so any difference between water supplied and sewer volume is assumed to have been discharged into the harbor. Between January 2012 and March 2015, SFS discharged an average of 24,200 CCF into the harbor monthly. 91.4% of water supplied was discharged into the harbor. Between April 2015 and October 2018, SFS discharged an average of 21,300 CCF into the harbor monthly, but 99.9% of water supplied was discharged into the harbor. This abrupt change to less water use but more of it being discharged to the harbor can be explained by the cessation of research activities that discharged water into the sewer system.
Because SFS discharges such a large volume and large percentage of its water to the harbor, more study into this area is necessary.
Stormwater runoff: In 2013, UWM researchers published "UWM as Zero-Discharge: Pondering Net-Positive Stormwater Infrastructure," which estimated that during a 100-year storm event, main campus has a stormwater runoff rate of 120 cubic feet per second. It also estimated that before any European settlement occurred, the same magnitude of storm would have produced 30 cubic feet per second of runoff. UWM can attempt to return to this pre-settlement hydrology by decreasing impervious surfaces, increasing stormwater storage capacity, and increasing the amount of deep-rooted native vegetation on campus.
Change in storage in cisterns: As noted in 1.3.2, the cisterns on main campus have a storage capacity of 55,710 gallons, or 74.47 CCF. They increase the volume of water stored on campus and reduce peak flows, but since no active controls or monitoring exist, their impact is modeled rather than measured, and is discussed. Optimizing the performance of green infrastructure in general is a growing field of research and could be undertaken by engineering or freshwater sciences students at UWM.
Change in storage in groundwater: This factor has not been measured and is difficult to estimate. Multiple studies have shown that the effects of urbanization such as the increase of impervious surfaces, the replacement of deep-rooted native vegetation with turf grass, and soil compaction reduce groundwater recharge. These factors can cause increased runoff during major rain and snowmelt events, leading to flooding and increased erosion in streams and rivers. Conversely, river levels tend to drop during dry periods due to a decrease in groundwater recharge. The University has undertaken multiple efforts to increase pervious surfaces and plant more native plants and trees. The effects of these efforts are difficult to quantify and could be the subject of further study.
The website URL where information about the programs or initiatives is available:
Additional documentation to support the submission:
Data was compiled from the Water Stewardship Plan that students completed in the Spring of 2019.